Visualizing Hash Match Joins

Bert Wagner continues his series on visualizing physical join operators:

Hash Match joins are the dependable workhorses of physical join operators.
While Nested Loops joins will fail if the data is too large to fit into memory, and Merge Joins require that the input data are sorted, a Hash Match will join any two data inputs you throw at it (as long as the join has an equality predicate and you have enough space in tempdb).  

Bert has some great animated GIFs too.

Related Posts

Blaming the Right Cardinality Estimator

Arthur Daniels helps us figure out which of SQL Server’s cardinality estimators your query used: SQL Server 2008 is reaching end of support this year, so upgrading your SQL Server might be on your mind. One of the big changes when you upgrade your SQL Servers is upgrading the compatibility level, which by default will […]

Read More

Optimizer Imperfections With Complex Filters

Erik Darling shows a couple examples of how the optimizer will sometimes pick a superior plan when dealing with complicated filters but not always: Sometimes, the optimizer can take a query with a complex where clause, and turn it into two queries. This only happens up to a certain point in complexity, and only if […]

Read More

Categories

January 2019
MTWTFSS
« Dec Feb »
 123456
78910111213
14151617181920
21222324252627
28293031